Mark Hay, a subsea supervisor, said on the night of the rig accident he was in bed and was awakened by an alarm.

Hay told the joint investigation board — led by officials from the Coast Guard and the Bureau of Ocean Energy Management, Regulation and Enforcement — that it may have been the general alarm, but he wasn’t sure. He said he heard a “bing, bing, bing” and that he believed it occurred before he heard an explosion.

Earlier testimony revealed that the three-way alarm, which warns of fire, combustible gas and toxic gas, had been on a manual setting, which limited it to certain areas such as the bridge. The general alarm could then be triggered by employees if required.

Transocean worker Mike Wiliams testified last month that he didn’t like the idea of inhibiting the safety system. Williams said, he had no warning of the explosion before it occurred.

At Monday’s hearing, Transocean’s Daun Winslow also said he had not heard alarms at the time of the accident, but he noted that noise from the blast and fire was too loud for him to hear much else.